Somali Islamist rebels have denied lifting a ban on certain aid groups in drought-affected areas and rejected the UN's claim that there is a famine in the region.

The rebel group al-Shabab, which controls much of southern Somalia, had said earlier this month that it would allow all humanitarian groups access to assist with the drought response. But al-Shabab spokesman Sheikh Ali Mohamud Rage has told a local radio station that the ban on specific aid agencies, which was imposed in 2009 and 2010, still stands. At the time, the rebels accused various humanitarian groups, including the UN's World Food Programme (WFP), which is expected to lead the current drought response, of damaging the local economy, being anti-Muslim, and of spying for the government.

"Those earlier banned groups are not welcome to serve in our area of control," Rage said on Friday.

Successive poor rainy seasons have caused a hunger crisis across the Horn of Africa, where 11 million people urgently need food aid. The situation is most acute in Somalia due to the ongoing conflict between pro-government forces and the al-Shabab rebels, as well as the Islamists' mistrust of outside help. The UN this week declared famine in two regions, Lower Shabelle and Bakool, which are both largely under the insurgents' control.

In a media briefing on Thursday evening in Mogadishu, Rage accused the UN of ulterior motives, and said that there was no famine.

"We say [the UN declaration] is totally, 100% wrong and baseless propaganda. Yes there is drought, but the conditions are not as bad as they say. They have another objective and it wouldn't surprise us if they were politicising the situation."

The WFP plans to airlift food within the next few days into Mogadishu, to where many people have fled from the countryside due to hunger. The organisation is also looking at ways of getting food into the famine-hit areas if it can get assurances that its staff will not be harmed and aid will not be diverted. David Orr, spokesman for the WFP in Nairobi, said the organisation had not received any official communication from al-Shabab that the ban was still in place.

"We are taking at face value the original statement that all humanitarian agencies will be allowed back in, and are proceeding on that basis. Our imperative remains getting into the famine zone as quickly as possible."